Neutron diffraction and Mossbauer study of the magnetic structure of HoFe6Sn6

We have used Time-or-Flight (ToF) neutron powder diffraction, and both Fe-57 and Sn-119 Mossbauer spectroscopy, to study the independent magnetic ordering behavior of the Fe and Ho sublattices in HoFe6Sn6. The crystal structure of HoFe6Sn6 is orthorhombic (space group Immm). The Fe sublattice orders antiferromagnetically with a Neel temperature of 559(5) K, determined by differential scanning calorimetry. The ToF neutron diffraction patterns obtained at 30 K and 295 K show that the antiferromagnetic ordering of the Fe sublattice is along [100] with a propagation vector q = [010]. The magnetic space group of the Fe sublattice is Ipm 'm 'm ' and the Fe magnetic moment at 30 K is 2.31(5) mu (B). This magnetic structure is confirmed by our Sn-119 Mossbauer spectra in which 37% of the Sn nuclei experience a substantial transferred hyperfine field from the Fe sublattice while the remaining 63% of the Sn sites show no magnetic splitting, due to the cancellation or transferred hyperfine fields from the Fe neighbors, in full agreement with our Wigner-Seitz cell calculations for each of the eight Sn sites in the HoFe6Sn6 structure. The Ho sublattice orders ferromagnetically at 9(1) K. ToF data obtained at 4 K show that the Ho moments are aligned along [001] i.e., perpendicular to the Fe ordering. The magnetic space group of the Ho sublattice is Im 'm 'm. The refined Ho magnetic moments at 4 K are 4.4(2) mu (B) and 5.2(2) mu (B) at the 2a and 4h sites, respectively.